1. Field of the Invention
The present invention relates in general to uninterruptible power supplies for critical equipment, and more specifically relates to a conditioning circuit operating from multiple redundant power sources that is preferably utilized to provide uninterrupted power to a power supply for control of aircraft display and control systems.
2. Description of the Prior Art
Advanced system technology utilized in modern aircraft requires reliable and tightly regulated power supply voltages. However, aircraft power distribution frequently contains voltage spikes and surges, brown-outs, and black-outs due to power bus transfer switching and various environmental conditions. Nevertheless, to maintain proper operation, power interruptions must be eliminated and the power supplied to the aircraft display system circuitry must be free from variations and glitches which might otherwise cause serious functional breakdowns in the operation of the equipment.
To provide power supplies useable with the critical equipment of aircraft systems, means have long been adopted to supply such power supplies with back-up features to improve their reliability. One such back-up feature is the utilization of energy storage circuitry sufficient to operate through short duration power interrupts. Another means for avoiding power supply interruptions, is the use of designs which operate from redundant d.c. input sources, each of which independently develops the output power that is required. These independently developed sources of power can then be utilized to insure that power is provided to a load without interruption. An example of one such prior art system is disclosed in U.S. Pat. No. 4,558,230. A power supply is disclosed in such patent that utilizes a dual source and power converter whereby either source and power converter is capable of powering the load upon failure of the other source or power converter and where the sources and power converters share the load if both sources are operative.
The uninterruptible conditioning circuit of the present invention differs from the prior art in that it is not a regulating power supply, but rather a special power conditioning circuit alternatively connecting a 28 volt primary source of power or a 24 volt battery source of power to a d.c. to d.c. converter such as a power supply. In this way, short duration interruptions of input power to the d.c. to d.c. converter are avoided through the use of a circuit design that is highly reliable, but is relatively simplistic in terms of components.